Relative size perception at a distance is best at eye level

Abstract

Relative size judgments were collected for two objects at 30.5 m and 23.8 m from the observer in order to assess how performance depends on the relationship between the size of the objects and the eye level of the observer. In three experiments in an indoor hallway and in one experiment outdoors, accuracy was higher for objects in the neighborhood of eye level. Weconsider these results in the light of two hypotheses. One proposes that observers localize the horizon as a reference for judging relative size, and the other proposes that observers perceive the general neighborhood of the horizon and then employ a height-in-visual-fieldheuristic. The finding that relative size judgments are best around the horizon implies that information that is independent of distance perception is used in perceiving size.Size constancy and size perception at a distance are old problems with theoretical implications for the nature of the perceptual process. Is perception ofsize derived inferentially from information about distance? Does perception of size rely on the general characteristics of the terrestrial environment in which we evolved? The current studies focus on the use ofone source ofinformation about the relative size of objects at a distance: the horizon line.In this paper, we first consider the geometry ofhorizon information about size and discuss the various ways horizon information could be used for size perception. We then present a set ofstudies that examine how horizon information influences relative size perception. Our methodology avoids the complications that come with involving changes in perceived distance. We propose that, if the horizon is used as a reference for perceiving relative size, observers should better discriminate small height differences near this reference.Before we can assess the role of horizon information about size, we need to consider the different ways in which an observer can use the horizon. For a standing observer viewing objects on the same ground plane, the explicit or implicit horizon line intersects objects at the observer's eye height, thereby specifying the absolute size ofthe object as a multiple of the observer's eye height (Sedgwick, 1973). This size information is independent of the distance of the object from the observer. Sedgwick (1973) was the first to observe that absolute size information is This research was supported by NIMH Grant MH52640-02 and NASA Grant NCC 2-925. We thank Eric Pranzarone and Stein Kristensen for assistance in data collection and Geoffrey Bingham, Ulric Neisser, and H. A. Sedgwick for comments on an earlier version of this article. Address correspondence to M. Bertamini, Staffordshire University, Psychology Division, College Road, Stoke-on-Trent ST4 2DE, England (e-mail: m.bertamini@staffs.ac.uk) or to T. L. Yang, Gilmer Hall, Department of Psychology, University of Virginia, Charlottesville, VA 22903 (e-mail: yang@virginia.edu). available in units ofthe standing observer's eye height, as is shown in the following formula:where H is object height as...

Memory for target height is scaled to observer height

“…That is, EH may be the default scalar for objects within EH range. This notion is consistent with studies in visual perception, in which participants scaled target heights to EH even in the absence of an explicit intended action (Bertamini et al, 1998;.…”

“…All parallel contours in a scene (except those normal to the line of sight) converge at the horizon, and for a forward-moving observer, all optically specified texture elements above EH move up, whereas those below EH move down. Bertamini, Yang, and Proffitt (1998) showed that observers are sensitive to EH when making relative height judgments. Their participants viewed two targets simultaneously and judged which target was taller.…”

“…EH, which coincides with the horizon, is one source of information that is especially useful in perceiving the relative sizes of objects (Bertamini, Yang, & Proffitt, 1998;Sedgwick, 1973). Perspective structure and optic flow define EH as a boundary such that EH creates a discontinuity in space.…”

Tool Use Affects Perceived Distance, But Only When You Intend to Use It.

“…Thus, eye height can provide a body-scaled metric for perceiving size. Bertamini, Yang, and Proffitt (1998) demonstrated that eye height provides a metric for relative size perception of objects viewed at a distance. They varied object height and egocentric distance, and perceivers judged which of two objects was taller.…”

Gender differences in spatial perception of body tilt

“…Perrone (1982) has proposed a general model that explains the overestimation of visual slant as due to the misperception of eye level relative to the hill. Other research has provided related computational models that demonstrate that the perception of relative size is influenced by angular declination and eye level (Bertamini, Yang, & Proffitt, 1998;Ooi, Wu, & He, 2001). Proffitt et al (1995) and Bertamini et al also confirmed that hills are generally experienced as being steeper than they actually are, although hills are not judged to be so when haptic or motoric assessments are used.…”